română GONZÁLEZ-FÉLIX JULIO CESAR, MENDOZA-RANGEL JOSÉ MANUEL, DIAZ-PEÑA ISMAEL, FÉLIX-MEDINA JENNIFER VIANEY
Abstract
The addition of Polypropylene Microfibers (PM) to an Ordinary Portland Cement (PC) based mortar with a substitution by weight of ground Fly Ash (FA) promotes a decrement of the angle of internal friction (Φ) in a cementitious matrix of the repair mortar and an increment of the cohesion (c) value in the interface between the substrate and the repair mortar zone. Mixtures samples were prepared by replacing cement by fly ash at 0% and 20% by weight, additions of polypropylene microfibers at 0% and 5% and compared with a reference mixture. The characterization of raw materials was carried out by Scanning Electron Microscopy (SEM) with Secondary Electrons (SE) for morphology, Backscattering Electrons (BE) for chemical composition and Energy Dispersive X-Ray Spectroscopy (EDS) for elemental analysis. Substrate and repair mortars were tested for compressive strength, indirect tensile strength, Young’s Modulus, Poisson Coefficient to study the mechanical behavior of the specimens. Electrical resistivity and carbonatation depth (concentration 4%, relative humidity 60 +/- 5%) were analyzed to study the durability of the samples. Samples with FA show a slightly decrement of the cohesion of the interface but samples with PM show an increment of this value, resulting in a higher cohesion with only PM. The use separately of FA and PM promote a lower angle of internal friction than reference samples. The results obtained under the experimental conditions used in this work, show that there is a synergistic effect between the use of polypropylene fibers and the pozzolanic material to reduce the carbonation depth caused using only the microfibers in the mixture.
Keywords
Fly Ash, Repair Mortar, Mechanical Properties, Polypropylene Microfibers, Durability, Cement Base Materials
SANG-SOON PARK
Abstract
Concrete sewer pipe line is one of the important civil infrastructures. Since the concrete sewer pipe is buried underground, the deterioration could be serious problem in maintenance and the repair and replacement cost is very high. The main aggressive factor affecting the durability of concrete sewer pipe is chemical attack by chloride and sulfate, so the sulfate resistant concrete should be used for the construction of sewer pipe line. In this study, the feasibility for the application of ferronickel slag powder (FSP) as a supplementary cementing material (SCM) used to improve the performance of concrete sewer pipe was investigated and the experimental tests were performed with different replacement ratio and fineness to determine the optimum level of replacement securing the improved chemical resistance and durability. The improvement of durability and chemical resistance of FSP contained mortar was verified through accelerated chloride ion penetration test, chemical resistance test and microstructural analysis. The optimum replacement rate of FSP can be considered as 40 % to assure the durability of concrete sewer pipe.
Keywords
concrete sewer pipe; ferronickel slag powder; durability; chemical resistance
SAFIA KHENGAOUI, MOULOUD ABDESSEMED, SAID KENAI, NOUREDDINE OUADAH
Abstract
In many countries, linear infrastructures (roads, railways or airports) are the most efficient and advantageous means of transport for citizens. Some of these infrastructures, such as roads or runways, are made of concrete, and as they are exposed to repeated loads and weather conditions, cracks are forming and spreading throughout the pavement. Several repair techniques have been applied to ensure their continued use under various types of traffic. The repair technique of adding lightweight welded mesh or geosynthetic layers seems to be a suitable solution, given their mechanical and aesthetic performance. This paper presents an experimental study on the effect of wire mesh and geogrids on the reinforcement of rigid concrete pavements. Twenty-four (24) specimens of concrete slabs, unreinforced and reinforced with a combination of geogrid sheets and wire mesh, were fabricated and tested in four-point bending. Validation of the experimental results was obtained by applying the finite element method, using a commercial software. Non-destructive in situ tests with a heavy deflectometer (HWD) were carried out on the central part of a rigid runway located in southern Algeria (arid zone), before and after its reinforcement with geogrids. It was found that geogrids are more effective than wire mesh in terms of tensile strength, stress and displacement reduction and downward crack propagation, with percentages ranging from 15 to 30%.
Keywords
Pavement, rigid, geogrid, wire mesh, reinforcement, experimentation, HWD, numerical
RASIM CEM SAKA, HALIT YAZICI
Abstract
In this study, LC30 structural lightweight concrete and LC60 high performance structural lightweight concrete were produced by using completely pumice aggregate. A total of 6 mixture designs were created by substituting 40% fly ash (FA) by weight into cement and adding 5.5 kg/m3 polypropylene fiber (PPF) to two different lightweight concrete designs. Flexural strength, compressive strength, total water absorption, electrical resistivity, rapid chloride ion penetrability tests were carried out on the produced concretes, and SEM-EDS analyzes were performed. As a result, lightweight structural concretes with a unit weight below 2000 kg/m3 could be produced by using 100% pumice aggregate, and LC60 high-performance lightweight concrete exhibited superior performance in all mechanical and physical tests compared to LC30 lightweight concrete. Since pumice has a porous structure, it has been confirmed by SEM images that there is a good interface between the aggregate and the matrix.
Keywords
Pumice, Fly ash, Synthetic fiber, Structural lightweight concrete, Lightweight aggregate
DAN PAUL GEORGESCU, CLAUDIU MAZILU, ADELINA APOSTU, ALIN BARBU
Abstract
The use of recycled aggregates is an efficient method and an important component for the sustainable development of the field of reinforced concrete constructions. Considering the particularities of concrete prepared with recycled aggregates, related to the origin of the aggregates but especially to the adherent mortar layer, in European regulations their use is restricted according to the exposure classes of the concrete. This limitation is due to the lower performance regarding the durability of concrete made with recycled aggregates, which in certain cases also requires a pretreatment operation. The research carried out, presented in this article, highlighted the particularities of the strength and durability characteristics of concrete prepared with recycled aggregates with and without the use of microsilica and nanosilica. By applying some experimental performance methods to evaluate the durability of concrete, it was possible to optimize the composition of concrete prepared with recycled aggregates. Also, in the case of the use of silica, the improvement of the performance of the concrete has been demonstrated, as well as the possibility of increasing the percentage of recycled aggregates used in its preparation, compared to that indicated in the current regulations.
Keywords
concretes, micro and nanosilica, recycled concrete aggregates, durability
Machine learning based prediction of compressive strength in concrete incorporating synthetic fibers
R. TUĞRUL ERDEM, AYBİKE ÖZYÜKSEL ÇİFTÇİOĞLU, ENGİN GÜCÜYEN, ERKAN KANTAR
Abstract
Different types of fibers are added to the concrete mixture to improve its behavior under different loading cases. This study intends to investigate the compressive strength of concrete cubic samples in which synthetic macro fibers are added in different amounts. For this purpose, a total of 72 cubic samples are produced in the experimental program. Axial pressure test is applied to cubic samples and 7 and 28 days compressive strength values are obtained in the end. However, a lot of effort has been spent to complete the time-consuming laboratory tests. To overcome this situation, four machine learning methods—Xgboost, Random Forest, Decision Tree, and Multiple Linear Regression—are adapted for efficient compressive strength forecasting. Moreover, four metrics are employed for a more meaningful evaluation of models: R2, RMSE, MAE, and MAPE. Remarkably, all models achieved R2 values exceeding 90%, with Xgboost notably reaching an impressive R2 value of 97%. This highlights the effectiveness of integrating machine learning in predicting compressive strength, offering a viable alternative to traditional laboratory tests. Incorporating the Shapley Additive exPlanation (SHAP) method, the study provides a detailed analysis of the models interpretability. SHAP analysis revealed that "Day" and "Fiber" have been identified as crucial features influencing compressive strength predictions. Localized SHAP analyses for specific samples further enhanced the understanding of individual predictions, emphasizing the practicality and transparency of machine learning in structural engineering. The promising results of this study indicate the potential for further advancements in enhancing performance, utilizing machine learning insights.
Keywords
Concrete; synthetic fibers; compressive strength; machine learning; Xgboost
TAIZHI XIANG, PENG ZHAO, WEIXING HOU, HAIYOU SHEN, ZIQUAN ZHAI, JINYUAN WANG, XINCHAO YE
Abstract
The development of Sea Water Sea Sand Concrete (SWSSC) holds critical importance for maritime engineering, especially given China s extensive marine resources and the potential they represent. Despite its promise, the utilization of SWSSC has been impeded by the corrosive nature of certain ions present within its constituents. The depletion of freshwater river sand coupled with advancements in construction material technology has reignited interest in SWSSC, prompting a reassessment of its viability. This review delineates the achievements in developing SWSSC, examining both the microstructural and macroscopic properties of key Supplementary Cementitious Materials (SCMs) such as seawater, sea sand, cement, fibers, and mineral admixtures. Each material s benefits and drawbacks are critically analyzed, with a focus on how they influence the concrete s durability and structural integrity. Furthermore, the review identifies existing gaps in research and offers direction for future investigations aimed at overcoming the challenges posed by corrosive elements and optimizing material properties for enhanced performance. The integration of innovative materials and techniques is proposed as a means to advance the practical application of SWSSC in building resilient marine infrastructure.
Keywords
Sea Water Sea Sand Concrete (SWSSC); Cement; Supplementary Cementitious Materials (SCMs); Fibers